In a conventional remote engine starting system such as disclosed in JP 3,475,769, an immobilizer unit outputs an engine start permission signal to an engine control unit to permit an engine starting, when an engine start command signal is output from an ignition key. The engine is then started when the ignition key is turned to a starter-on position of a starter switch. Further, the immobilizer unit outputs the engine start permission signal to the engine control unit to permit the engine starting, when an engine start command signal is output from a remote controller, which is a portable transmitter. Thus, the engine can be started from an outside of a vehicle.
When the immobilizer unit outputs no engine start permission signal, it normally provides an indication of vehicle travel prohibition to indicate that an immobilizer system for protecting a vehicle from unauthorized use is set in operation. When the immobilizer unit provides its engine start permission signal, it provides no such indication.
Since the indication of vehicle travel prohibition is cancelled and the engine is started in response to the engine start permission signal, the indication is also cancelled and the engine is also started when the remote controller outputs its engine start permission signal. In this occasion, the user of the vehicle may not be present close to the vehicle and may be away from the vehicle until the engine is warmed up sufficiently. It is thus likely that an unauthorized user breaks a window or a door and steals the vehicle.